I live near an Interstate highway. I have seen the same deer herds on both sides of the Interstate, yet have never seen them cross. In addition there has never been a deer hit by a car for twenty miles in either direction. I decided to investigate.
The deer are traveling under the Interstate through dry storm drains. These tunnels are about eight feet square and a hundred yards long. The bottoms are covered with about eight inches of sand....deposited by water running through them, I assume. Hundreds of tracks, both coming and going.
I decided to walk through one of them. No problemo, as I could see a tiny square of light at the other end. About half way through it was darker than the inside of a cow. Couldn't see my hand in front of my face but it was too late to turn back. Started to imagine all kinds of snakes and other evil things. I won't do that again, at least not without a flashlight.